Grokking the System Design Interview
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Alex T
N = 5 example

Alex T

Nov 22, 2024

I'm not sure I understand the sentence:

  • Read and Write Quorums: For read and write operations, different quorum sizes can be defined. For example, a system might require a write quorum of 3 nodes and a read quorum of 2 nodes in a 5-node cluster.

From this sentence, it seems like N = 5, W = 3 and R = 2. However, it was previously stated that you need the condition N < R + W?

The condition 5 < 2 + 3 is false.

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 Vladyslav
Vladyslav2 months ago

Yes, I'm also confused; it looks like an error. When W = 3, R = 2, and N = 5, it doesn't satisfy the R + W > N rule. We could write data to 3 nodes and read from 2 outdated nodes, which would result in inconsistent data

It look, the correct phrase should be:

  • **Read...